#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

#define MAXN 25

long long f[MAXN][MAXN] = {0};

int ctrl[MAXN][MAXN] = {0}, n, m, hx, hy;

const int dx[] = {0, -2, -1, 1, 2, 2, 1, -1, -2};
const int dy[] = {0, 1, 2, 2, 1, -1, -2, -2, -1};

int main() {
	cin >> n >> m >> hx >> hy;
	for(int i = 0; i <= 8; i++){
		int tmpx = hx + dx[i],   tmpy = hy + dy[i];
		if(tmpx >= 0 && tmpx <= n && tmpy >= 0 && tmpy <= m)
			ctrl[tmpx][tmpy] = 1;
	}
	f[0][0] = 1;
	f[0][0] = 1 - ctrl[0][0];
	for(int i = 0; i <= n; i++){
		for(int j = 0; j <= m; j++){
			if(ctrl[i][i])	continue;
			if(i)	f[i][j] += f[i - 1][j];
			if(j)	f[i][j] += f[i][j - 1];
		}
	}
	cout << f[n][m] << endl;
	return 0;
}